Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/52—Two layers
  • B05D7/54—No clear coat specified
  • B05D7/546—No clear coat specified each layer being cured, at least partially, separately
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
  • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2506/00—Halogenated polymers
  • B05D2506/10—Fluorinated polymers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2508/00—Polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
  • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree
  • Y10T428/2495—Thickness [relative or absolute]
  • Y10T428/24967—Absolute thicknesses specified
  • Y10T428/24975—No layer or component greater than 5 mils thick
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/263—Coating layer not in excess of 5 mils thick or equivalent
  • Y10T428/264—Up to 3 mils
  • Y10T428/265—1 mil or less
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/266—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension of base or substrate

Definitions

• ABSTRACT A firmly adhering coating on a metal includes a baked base layer whose binder component is a linear polyester resin and a hardener for the same, and a baked surface layer essentially consisting of to percent of the polyester resin employed in the base layer and 60 to percent polyvinylidene fluoride.
• Coatings of pure polyvinylidene fluoride have been applied to metals heretofore, but they showed only poor adhesion to the substrate. It has been attempted to improve adhesion by interposing a primer between the metal and the polyvinylidene fluoride layer, such as an epoxy resin primer containing polyvinylidene fluoride or corresponding primers partly based on special acrylic resins or aldehyde-modified acrylamide polymers.
• the epoxy resin primers have a very short pot life when mixed with the necessary catalyst while the acrylic primers are so inferior to polyvinylidene fluoride in their mechanical, thermal, and chemical properties as to reduce the overall quality of the laminar coatmg.
• the primary object of the invention is the provision of a polyvinylidene fluoride coating for metals which is free of the shortcomings of the afore-described, known laminar coatings and provides the unimpaired advantages of polyvinylidene fluoride as a coating material.
• the coatings of the invention include a baked base layer whose binder components are a saturated, linear polyester and a hardener therefore, and a surface layer whose binder component essentially consists of to 40 percent of the aforementioned polyester and 60 to 90 percent polyvinylidene fluoride. All the foregoing percentage values referred to in this application and the appended claims are by weight unless otherwise specifically stated.
• the two layers are applied sequentially to the degreased or otherwise prepared metallic substrate by spraying, brushing, rolling of their solutions, or dispersions in a conventional manner, and are cured by baking at an elevated temperature at which the solvents present evaporate.
• the dispersing media employed are individual solvents or solvent mixtures in which the polyester employed is dissolved and which have desirable evaporation rates for forming an intimate mixture of the polyester and the polyvinylidene fluoride in the surface layer.
• Suitable solvents include ketones (methylethylketone), esters (dimethyl phthalate, methyl acetate, ethyl acetate, ethyl acetoacetate, methylglycol acetate,
• halogenated hydrocarbons methylene chloride
• aromatic hydrocarbons benzene, toluene
• cyclic ketones cyclohexanone, isophoron
• amides of carboxylic acids dimethylformamide
• Dimethyl phthalate and/or methylglycol acetate have been found most advantageous, and may be further combined with low-boiling organic solvents, such as chloroform, benzene, methylene chloride, and the like, which facilitate the establishment of desired processing conditions.
• Hydrocarbons also their halides, are employed in combination with polar solvents.
• polyesters may-be employed, those having aromatic acid moieties and aliphatic alcohol moieties being preferred.
• the sole qualifications required of the polyester used for this invention are good solubility, and the ability of being cured at elevated temperature to fonn a layer of lacquer.
• polyester a neutral, saturated, linear polyester obtained from an aromatic dicarboxylic acid and an aliphatic diol, having an average molecular weight of 18,000 to 20,000,'a melting range of to C, a hydroxyl number of 5 to 10 (as determined by the method of Norman and Schildknecht: Fettchem. Rundschau 40, 194), and an acid number of 0 3, as determined by German Industrial Standard DIN 53 183.
• Polyester having the desired characteristics are staple articles of commerce (Dynapol L 206, manufactured by Dynamit Nobel, for example).
• the average molecular weight may range from 15,000 to 25,000, and the melting range from 70 to 200C without major loss in coating properties.
• the polyester is hardened by addition of conventional hardeners, such as melamine or guanamine resins, urea resins, and polyurethanes.
• conventional hardeners such as melamine or guanamine resins, urea resins, and polyurethanes.
• the base layer is preferably applied at a rate to produce a dry, cured film 2 to 20 pm thick, best results being usually obtained with films having a thickness of 5 to 12 pm.
• the permissible lower limit of base layer thickness is a function of the desired adhesion of the surface layer to the substrate, and should be determined experimentally if a very thin base layer, such as one thinner than 2 pm, should be preferred.
• An upper limit of thickness cannot be established by technical criteria, but is a matter of convenience and economy. No further improvement in the adhesion of a surface layer can be achieved by making the base layer thicker than 20 um. However, heavier base layers may be resorted to for leveling the surface of a rough substrate.
• the polyvinylidene fluoride-bearing surface layer may be applied at any time after the curing or baking of the base layer.
• the polyvinylidene fluoride is dispersed in the liquid medium in the form of finely ground particles having a primary particle size of l um or less.
• the preparation of a suitable grade of polyvinylidene fluoride has been described, for example, in the published German Pat. application No. 1,939,852.
• Vinylidene fluoride is polymerized at elevated temperature and pressure in an acidic aqueous medium in the presence of a peroxydisulfate catalyst and at an initiator concentration of less than 0.5 g/l liquid mixture.
• the surface layer when dry, should have a thickness of 5 to 50 um, preferably 20 to 30 pm, but surface layers that are thinner or thicker may be found useful under special conditions. When the lower thickness limit is not reached, the desirable properties of polyvinylidene fluoride may not be fully available.
• polyester component of the surface coating should satisfy the same requirements as those pointed out above with reference to the base layer. Different polyesters may be employed in the two superposed layers, but the polyester used in the surface layer, if different from that in the base layer, should satisfy the molecular weight and melting range requirements set forth above.
• the laminar coating in addition to its essential ingredients described above, may also contain thermally stable pigments, preferably oxides of the transition metals, and particularly titanium dioxide.
• the pigments may be employed jointly with a wetting agent for better wetting of the pigment by the binder. Amphoteric wetting agents have been found most suitable.
• the coating compositions may further include additives conventional in organic coatings such as adhesionimproving, gloss-enhancing, and delustering agents.
• the two lacquer compositions respectively employed in forming the base and surface layers of the coating are sequentially applied in a wet thickness sufficient to yield the desired dry fllm thickness, and individually cured or baked under conditions suitable for the specific compositions.
• the curing time may be 0.5 to 2 minutes at 250 300C oven temperature.
• the metal surfaces to be coated are prepared for coating in a known manner. They are at least degreased. When the substrate is steel, it may be coated with zinc or receive chromate and/or phosphate conversion coatings. Aluminum is preferably given a chromate conversion coating such as alodizing.
• the laminar, organic coatings of the invention combine the known, superior properties of polyvinylidene fluoride and of polyester in a most satisfactory manner so that the coatings have excellent adhesion and have sufficient resiliency to permit severe deformation of the substrate without peeling or other separation.
• the coatings are chemically inert, weather resistant, and do not yellow when exposed to light. They are eminently suitable for protecting articles exposed to the atmosphere. Howevcr, they have also been used successfully for lining pipes, storage containers, chemical reactors, and electroplating racks.
• Base layer compositions Nos. 1 to 7 were prepared by dissolving the polyester described above (Dynapol 1.. 206), with or without an amphoteric wetting agent (Troy-98-C), in solvent at 70C. As far as a pigment (TiO of rutile type) and a hardener was employed, the mixture was homogenized on a ball mill for 15 hours at ambient temperature (about 20C). The several compositions then were applied to metallic substrates as wet films 50 pm thick, and baked or cured at 250C for 2 minutes.
• Table 1 lists the percentage of polyester, pigment, hardener, and solvent in each composition, and the thickness of the dry base layer obtained after baking.
• the hardeners employed were melamine butyl ether, benzoquanamine formaldehyde resin (BFR), and toluenesulfonic acid.
• the solvents were dimethyl phthalate, methylethylketone, and methylglycol acetate, and
• the same polyester and wetting agent as described in Example 1 were dissolved at 70C in organic solvent, and the hardener and pigment, if used, and the polyvinylidene fluoride were dispersed in the polyester solution by grinding in a ball mill for hours at ambient temperature as in Example 1.
• the pigment was ground with the polyester solution for about 5 to 6 hours before the polyvinylidene fluoride was added and grinding continued for 15 hours longer.
• Table ll identifles the substrate employed with each surface coating No. 8 to 22 by a lower case letter.
• a indicates an aluminum alloy sheet, 1.5 mm thick, containing 1% Mg, degreased in an aqueous commercial cleaning solution at 70C for 30 seconds, etched, and alodized at 50C for 10 seconds.
• a zinc coated steel sheet, 0.75 mm thick, is indicated by b, whereas c refers to a steel sheet of equal thickness carrying a phosphate conversion coating.

Landscapes

• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Paints Or Removers (AREA)
• Laminated Bodies (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Adhesives Or Adhesive Processes (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=5812305

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (3)

Citations (5)

• 1971
  • 1971-06-30 DE DE2132645A patent/DE2132645C3/de not_active Expired
• 1972
  • 1972-06-27 IT IT69070/72A patent/IT959262B/it active
  • 1972-06-28 US US00267014A patent/US3798052A/en not_active Expired - Lifetime
  • 1972-06-28 GB GB3027072A patent/GB1364338A/en not_active Expired
  • 1972-06-29 NL NL7209011A patent/NL7209011A/xx not_active Application Discontinuation
  • 1972-06-29 CA CA146061A patent/CA936430A/en not_active Expired
  • 1972-06-30 FR FR7223869A patent/FR2143955B3/fr not_active Expired

Patent Citations (5)

Also Published As

Similar Documents

Legal Events